Question

I’m trying to find two patterns within an array and put the results into another array.

For example

  $/ = "__Data__";

  __Data__
  #SCSI_test         # put this line into  @arrayNewLines      
  kdkdkdkdkdkdkdkd
  dkdkdkdkdkdkdkdkd
  - ccccccccccccccc  # put this line into @arrayNewLines

Code

    while(<FILEREAD>)
    {
          chomp;
          my @arrayOld = split(\n,@array);

          foreach my $i (0 .. $#arrayOld)
          {
                if($arrayOld[$i] =~ /^-(.*)/g or /\#(.*)/g)
                {
                     my @arrayNewLines = $arrayOld[$i];
                     print "@arrayNewLines\n";
                }
          }
    }

This code only prints out only ccccccccccccccc
But I would like it to output ccccccccccccccc #SCSI_test

Answer 1

That code does not print just cccccc..., it prints everything. Your problem is this line:

if($arrayOld[$i] =~ /^-(.*)/g or /\#(.*)/g) {

What you are doing here is first checking $arrayOld[$i] and then checking $_, because /\#(.*)/ is perl shorthand for $_ =~ /\#(.*)/. Since the line contains a hash character #, it will always match, and the line will always print.

Your line is equivalent to:

if(   $arrayOld[$i] =~ /^-(.*)/g 
      or 
      $_ =~ /\#(.*)/g) {

The answer there is to join the regexes:

if($arrayOld[$i] =~ /^-|#/) {

However, your code is far from clean after that… starting from the top:

If you set the input record separator $/ to __Data__ with that input, you will get two records (Data::Dumper output shown below):

$VAR1 = '__Data__';
$VAR1 = '
#SCSI_test         # put this line into  @arrayNewLines
kdkdkdkdkdkdkdkd
dkdkdkdkdkdkdkdkd
- ccccccccccccccc  # put this line into @arrayNewLines
';

When you chomp the records, you will remove __Data__ from the end, so the first line will become empty. So in essence, you will always have a leading empty field. This is nothing horrible, but something to remember.

Your split statement is wrong. First off, the first argument should be a regex: /\n/. The second argument should be a scalar, not an array. split(/\n/,@array) will evaluate to split(/\n/, 2), because the array is in scalar context and returns its size instead of its elements.

Also, of course, since you are in a loop reading lines from the FILEREAD handle, that @array array will always contain the same data, and has nothing to do with the data from the file handle. What you want is: split /\n/, $_.

This loop:

foreach my $i (0 .. $#arrayOld) {

is not a very good loop structure for this problem. Also, there is no need to use an intermediate array. Just use:

for my $line (split /\n/, $_) {

When you do

my @arrayNewLines = $arrayOld[$i];
print "@arrayNewLines\n";

You are setting the entire array to a scalar, then printing it, which is completely redundant. You get the same effect just printing the scalar directly.

Your code should look like this:

while(<FILEREAD>) {
    chomp;
    foreach my $line (split /\n/, $_) {
        if($line =~ /^-|#/) {
            print "$line\n";
        }
    }
}

It is also recommended that you use lexical file handles, so instead of

open FILEREAD, "somefile" or die $!;       # read with <FILEREAD>

use:

open my $fh, "<", "somefile" or die $!;    # read with <$fh>